Fig. 2. Expression of ß-galactosidase in Osr2 heterozygous embryos. (A) At E9.5, ß-galactosidase expression (blue) was detected specifically in the mesonephric vesicles (arrow). (B) At E10.5, ß-galactosidase activity was detected in the mesonephros (arrow), in the limb buds, in the maxillary and mandibular processes, in the mesenchyme posterior to the eye and in the mesenchyme adjacent to the first branchial cleft (arrowhead). (C) Facial view of a stained E10.5 embryo showing ß-galactosidase expression in the palatal primordia (arrowheads). (D,E) Frontal sections of E13.5 (D) and E14.75 (E) heterozygous embryos showing ß-galactosidase expression in the palatal mesenchyme, olfactory mesenchyme, tooth bud mesenchyme, and the periocular mesenchyme and the eyelids. e, eye; fl, forelimb bud; hl, hindlimb bud; mb, mandibular process; mx, maxillary process; oe, olfactory epithelia; p, palatal shelf, t, tongue; tb, tooth bud.